Process Bounced Email (Non-Delivery Report) and Email Tracking

For many email campaign applications, the very important task is detecting if the email is received by recipient or not.
Parsing the delivery report is the common way to get the email status. It is strongly recommend that you remove the invalid or non-existent recipient from
your mail listing to save networking resource.

SMTP Transport Error and Failure Report (NDS)

When you are sending an email to a recipient by EASendMail:

SMTP Transport Error

If you call SendMail method and this method throws an exception, this is a SMTP Transport Error
and you will not get Failure Report (NDS). In this case, you can get the error detail from the Exeception object.

Failure Report (NDS)

If you call SendMail method successfully, that means the email has been submitted to the SMTP server.
The SMTP server will deliver the email in background, if the email couldn't be delivered, a Failure Report (NDS) will be sent back to your
sender email address.

To retrieve and parse Failure Report (NDS), you should monitor your sender mailbox. We recommend that you use
EAGetMail Component to monitor your sender mailbox by POP3/IMAP4/Exchange WebDAV/Exchange Web Service protocol.
After you installed EAGetMail on your machine, there are several full samples named "parse_report.*" for VB.NET, C# in the installation path.

If there is no Failure Report arrived in 24 hours, that means the email
has arrived to user mailbox.

SMTP Transport Error and Failure Report are supported by all SMTP servers, so we strongly recommend that you catch SMTP Transport Error and
parse Failure Report (NDS).

Delivery Receipt

It is also called a DSN (delivery service notification), which is a request to the recipient’s email server
to send you a notification about the delivery of an email you've just sent. The notification takes the form
of an email, and will tell you if your delivery succeeded (Delivery Receipt), failed,
got delayed (Failure Report (NDS)).

Import Notice: Not every SMTP server support Delivery Receipt.
Only the SMTP server that supports DSN extension command accepts Delivery Receipient request, otherwise you will get error when you are sending email.

The following example codes demonstrate how to request read receipt and delivery receipt:

Email tracking is used to verify that emails are actually read by recipients. There are two common solutions:

Read Receipt

Some e-mail applications, such as Microsoft Office Outlook, employ a read-receipt
tracking mechanism. A sender selects the receipt request option prior to sending
the message. Upon opening the email, each recipient has the option of notifying
the sender that the message was opened and read.

However, there is no guarantee that you will get a read-receipt. Some possible reason
are that very few e-mail applications or services support read receipts, or simply
because users disable the functionality. Those do support read-receipt aren't necessarily
compatible with or capable of recognizing requests from a different e-mail service
or application.

Some email marketing tools include tracking as a feature.
Such email tracking is usually accomplished using standard web tracking devices known as cookies and web beacons.
When you send a tracked email message, if it is a graphical HTML message (not a plain text message) the email marketing system may embed
a tiny, invisible tracking image (a single-pixel gif, sometimes called a web beacon) within the content of the message.
When the recipient opens the message, the tracking image is referenced.

For example:
In your HTML body, you link a image to your website like this:
<img src="http://yoursite/trace.aspx?id=12323" />. When the user opens the email,
http://yoursite/trace.aspx?id=12323 will be accessed by user email client. Your trace.aspx can record the id to database to identify the email
to this user has been read and return a small image.

Security Issues

To prevent email marketers, spammers and phishers use tracking maliciously, almost 100% email client don't open the linked image directly.
The email client ususally asks the user if it should display the linked image, if the user answer "no", the tracking image will not be openned.
That means you can only trace the email under user permission, it is a good protection for user privacy.

Privacy Issues

Linked Image Tracking can sometimes reveal if emails get forwarded (but not usually to whom).
When used maliciously, it can be used to collect confidential information about businesses and
individuals and to create more effective phishing schemes.

If you are using email tracking, your company's privacy policy should
state that you may use tracking devices such as cookies and web beacons.

Firstly, SmtpClient performs a DNS MX record query.
If it retrieves the recipient's local SMTP server successfully, SmtpClient will try to connect to this server.
SmtpClient then performs "RCPT TO" command to test if this SMTP server accepts this email address.

Why we don't recommend testing email address?

Because it totally depends on your networking connection, if your networking connection to the recipient server is bad or your IP address
is blocked by the recipient server, test will be failed, but it doesn't mean this email address is invalid.

Moreover, to prevent email address testing, many email providers accept the recipient address at first no matter if the address is valid or invalid, only after you sent the email data
to the server, then the server rejects it if the recipient address is invalid.

Recommended Solution

Send the email to the recipient without testing. If you don't get Transport Error and Failure Report in 24 hours, that means the recipient is valid.
If you get Failure Report, you should consider to remove this recipient from your mail listing.